rootless: fail early if prerequiresites are not satisfied

`kind create cluster` now prints errors before running the containers.

Signed-off-by: Akihiro Suda <[email protected]>

pkg/cluster/internal/create/create.go

@@ -66,6 +66,11 @@ type ClusterOptions struct {
 
 // Cluster creates a cluster
 func Cluster(logger log.Logger, p providers.Provider, opts *ClusterOptions) error {
+	// validate provider first
+	if err := validateProvider(p); err != nil {
+		return err
+	}
+
 	// default / process options (namely config)
 	if err := fixupOptions(opts); err != nil {
 		return err
@@ -234,3 +239,19 @@ func fixupOptions(opts *ClusterOptions) error {
 
 	return nil
 }
+
+func validateProvider(p providers.Provider) error {
+	info, err := p.Info()
+	if err != nil {
+		return err
+	}
+	if info.Rootless {
+		if !info.Cgroup2 {
+			return errors.New("running kind with rootless provider requires cgroup v2, see https://kind.sigs.k8s.io/docs/user/rootless/")
+		}
+		if !info.SupportsMemoryLimit || !info.SupportsPidsLimit || !info.SupportsCPUShares {
+			return errors.New("running kind with rootless provider requires setting systemd property \"Delegate=yes\", see https://kind.sigs.k8s.io/docs/user/rootless/")
+		}
+	}
+	return nil
+}

pkg/cluster/internal/providers/docker/provider.go

@@ -51,6 +51,7 @@ func NewProvider(logger log.Logger) providers.Provider {
 // see NewProvider
 type provider struct {
 	logger log.Logger
+	info   *providers.ProviderInfo
 }
 
 // String implements fmt.Stringer
@@ -286,17 +287,39 @@ func (p *provider) CollectLogs(dir string, nodes []nodes.Node) error {
 
 // Info returns the provider info.
 func (p *provider) Info() (*providers.ProviderInfo, error) {
-	cmd := exec.Command("docker", "info", "--format", "{{json .SecurityOptions}}")
+	var err error
+	if p.info == nil {
+		p.info, err = info()
+	}
+	return p.info, err
+}
+
+// dockerInfo corresponds to `docker info --format '{{json .}}'`
+type dockerInfo struct {
+	CgroupVersion   string   `json:"CgroupVersion"` // e.g. "2"
+	MemoryLimit     bool     `json:"MemoryLimit"`
+	PidsLimit       bool     `json:"PidsLimit"`
+	CPUShares       bool     `json:"CPUShares"`
+	SecurityOptions []string `json:"SecurityOptions"`
+}
+
+func info() (*providers.ProviderInfo, error) {
+	cmd := exec.Command("docker", "info", "--format", "{{json .}}")
 	out, err := exec.Output(cmd)
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to get docker info")
 	}
-	var securityOptions []string
-	if err := json.Unmarshal(out, &securityOptions); err != nil {
+	var dInfo dockerInfo
+	if err := json.Unmarshal(out, &dInfo); err != nil {
 		return nil, err
 	}
-	var info providers.ProviderInfo
-	for _, o := range securityOptions {
+	info := providers.ProviderInfo{
+		Cgroup2:             dInfo.CgroupVersion == "2",
+		SupportsMemoryLimit: dInfo.MemoryLimit,
+		SupportsPidsLimit:   dInfo.PidsLimit,
+		SupportsCPUShares:   dInfo.CPUShares,
+	}
+	for _, o := range dInfo.SecurityOptions {
 		// o is like "name=seccomp,profile=default", or "name=rootless",
 		csvReader := csv.NewReader(strings.NewReader(o))
 		sliceSlice, err := csvReader.ReadAll()

pkg/cluster/internal/providers/podman/provider.go

@@ -19,6 +19,7 @@ package podman
 import (
 	"encoding/json"
 	"fmt"
+	"io/ioutil"
 	"net"
 	"os"
 	"path/filepath"
@@ -53,6 +54,7 @@ func NewProvider(logger log.Logger) providers.Provider {
 // see NewProvider
 type provider struct {
 	logger log.Logger
+	info   *providers.ProviderInfo
 }
 
 // String implements fmt.Stringer
@@ -347,8 +349,42 @@ func (p *provider) CollectLogs(dir string, nodes []nodes.Node) error {
 
 // Info returns the provider info.
 func (p *provider) Info() (*providers.ProviderInfo, error) {
+	var err error
+	if p.info == nil {
+		p.info, err = info(p.logger)
+	}
+	return p.info, err
+}
+
+func info(logger log.Logger) (*providers.ProviderInfo, error) {
+	euid := os.Geteuid()
 	info := &providers.ProviderInfo{
-		Rootless: os.Geteuid() != 0,
+		Rootless: euid != 0,
+	}
+	if _, err := os.Stat("/sys/fs/cgroup/cgroup.controllers"); err == nil {
+		info.Cgroup2 = true
+		// Unlike `docker info`, `podman info` does not print available cgroup controllers.
+		// So we parse "cgroup.subtree_control" file by ourselves.
+		subtreeControl := "/sys/fs/cgroup/cgroup.subtree_control"
+		if info.Rootless {
+			// Change subtreeControl to the path of the systemd user-instance.
+			// Non-systemd hosts are not supported.
+			subtreeControl = fmt.Sprintf("/sys/fs/cgroup/user.slice/user-%d.slice/user@%d.service/cgroup.subtree_control", euid, euid)
+		}
+		if subtreeControlBytes, err := ioutil.ReadFile(subtreeControl); err != nil {
+			logger.Warnf("failed to read %q: %+v", subtreeControl, err)
+		} else {
+			for _, controllerName := range strings.Fields(string(subtreeControlBytes)) {
+				switch controllerName {
+				case "cpu":
+					info.SupportsCPUShares = true
+				case "memory":
+					info.SupportsMemoryLimit = true
+				case "pids":
+					info.SupportsPidsLimit = true
+				}
+			}
+		}
 	}
 	return info, nil
 }

pkg/cluster/internal/providers/provider.go

@@ -51,5 +51,9 @@ type Provider interface {
 
 // ProviderInfo is the info of the provider
 type ProviderInfo struct {
-	Rootless bool
+	Rootless            bool
+	Cgroup2             bool
+	SupportsMemoryLimit bool
+	SupportsPidsLimit   bool
+	SupportsCPUShares   bool
 }